Voters in Washington state are making their choice for the Republican party presidential nominee.

The caucus in that western state Saturday comes ahead of the so-called "Super Tuesday" voting in 10 states that could determine who will face President Barack Obama, a Democrat, in November's election.

In the latest national poll (Gallup), former Massachusetts governor Mitt Romney has 35 percent support, while former U.S. senator Rick Santorum has 24 percent. The other candidates, former House speaker Newt Gingrich and Texas Representative Ron Paul, trail with 15 percent and 11 percent, respectively.

At stake in Washington are 40 delegates to the Republican national convention.